The invention relates to sensors for the measurement of chemical species. More particularly, the invention relates to simultaneous electrochemical detection of chemical species using sensors on a substrate.
Ion selective electrodes (ISE) are used in the analytical determination of basic chemical parameters of samples. ISE are able to meet strict requirements for low sample mass, rapid and continuous measurement that are imposed by operation in remote environments, such as onboard spacecraft. Generally, ISE allow the elimination of time-consuming sample preparation steps such as filtration, weighing and distillation, resulting in fewer systematic measurement errors, better standard deviation, and more accurate measurements.
ISE known in the art include recently developed carrier-based polymeric membrane ISE, the key components of which include: a lipophilic complexing agent, known as an ionophore, capable of reversibly binding an analyte; and a solvent polymeric membrane composed of a high viscosity, water-immiscible liquid. Polymer-based ISE using Ag+ instead of Clxe2x88x92 are known to produce more stable potentials where there are changes in pressure, concentration and temperature.
The deposition and/or modification of individual ISE sensors in an array by individually electronically addressing each ISE sensor, and using processes to dope the electrolyte with appropriate ions, is described herein. Such techniques allow an assembly of ISE arrays to be constructed that enable the use of neural nets and pattern recognition software, thereby increasing the quantity and quality of information obtained from the sensors.
The devices and processes described herein provide a number of advantages. For example, the devices allow simultaneous measurement of the presence of particular chemical species in a sample, and can give measurement of particular physical properties of the sample. Among these are identity and quantification of chemical species. The devices can monitor pH, the presence of inorganic species, organic species, gases, as well as monitoring conductivity and oxidation-reduction potential (ORP) of samples. The devices are also able to determine biological signatures of organisms or residual chemical mixtures characteristic of the presence of organisms.
The devices contain sensors which are made to a surface area density of up to 10 times that of conventional sensors, enabling more data collection. The devices are able to be constructed at lower cost than conventional chemical sensor arrays. The devices are highly portable, and suitable for use by individual consumers as well as by industrial entities.
The use of such devices in chemical, medical and pharmaceutical laboratories carries particular advantages, such as on-line process monitoring, industrial water quality monitoring, monitoring of biologically essential fluids in remote locations such as on board spacecraft, and the ability to conduct biological signature analysis for planetary systems, or on earth.
The processes used to create such devices represent the first application of directed deposition of spatially resolved species by electrical means. These processes also have the particular advantage of not using maskless processes to personalize the characteristics of individual sensors in the array. Maskless processes eliminate costly and environmentally undesirable steps such as photolithography, micro- or nanopipetting, or ink jetting of dopant molecules.
The devices described herein also include novel circuitry and methods of monitoring and carrying out deposition processes. The novel circuitry enables the use of potentiometric or galvanometric monitoring and deposition. These two modes can be chosen according to the wishes of the operator, and can be alternated when desired. Alternatively, the process can be switched by an automated switch, according to preset parameters.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.